1. Field of the Invention
The present invention pertains to the art of cooking appliances and, more particularly, to a system for controlling the heat output of a radiant heating device in a compact cooking appliance which is preferably capable of combining radiant, convection, conduction and microwave heating techniques to perform a cooking operation and can be connected to varying voltage supplies.
2. Discussion of the Prior Art
There exist a wide range of cooking appliances on the market. Many of these cooking appliances are designed for use in cooking various types of food products in different ways. For instance, where more conventional cooking appliances generally relied upon radiant energy as the sole heat source, more recent trends combine a radiant heat source with convection, microwave or conduction heating techniques, thereby increasing the versatility of the cooking appliance while potentially shortening required cook times. In particular, the prior art contains examples of appliances that combine radiant and convection cooking; convection, microwave and radiant cooking; and microwave, convection and conduction heating techniques.
Regardless of the existence of these known arrangements, there still exists a need for a cooking appliance that combines each of radiant, convection, microwave and conduction heating techniques in an efficient and effective manner to handle a wide range of food items. Particularly, there exists a need for a cooking appliance that can be used to rapidly prepare food products that require numerous different heat sources for full and complete cooking. For example, the rapid preparation of commercially produced, open-faced grilled sandwiches raises various cooking concerns. Open-faced grilled sandwiches require, at the very least, that heat be directed both downward onto an upper portion of the sandwich and upward onto a lower bun portion of the sandwich. In most cases this is accomplished by passing the open-faced sandwich on a conveyor belt through an oven between opposing radiant heat sources. While effective to a degree, the process can be time consuming and really does not result in a uniform heating of the meat, cheese and/or other toppings on the bread, nor an even toasting of the bread itself. In addition to this potential problem, a dual radiant oven of this type is simply not suitable for many other applications. For instance, an additional microwave oven or the like would typically be employed to heat soup or other liquid-based food items.
Regardless of the variety of known cooking appliances, there exists the need for a versatile cooking appliance that can preferably take advantage of radiant, convection, microwave and conductive cooking techniques such that the appliance can be used to rapidly and effectively cook a wide range of food items. When providing such a versatile cooking appliance, it is desirable to be able to operate one or more heating elements at a consistent intensity, even though the power supplied to the appliance may vary. In particular, a resistance heater is sized to provide a specific intensity for a specified AC voltage input. For example, a heating element may be rated at 900 watts for an input voltage of 208 volts AC. If less than the rated voltage is applied, the output heat of the heating element is correspondingly lowered. If more than the rated voltage is applied, an increase in the heat output will occur, while the useful life of the heating element will be shortened.
To address this concern, it is possible to provide a controller with structure that senses the input voltage and switches the output of a transformer, thereby enabling a consistent voltage to be sent to a heating element, such as a magnetron. Unfortunately, the added costs associated with such controller structure, as well as an automatic transformer, can be cost and/or weight prohibitive in connection with certain cooking appliances. For this reason, most cooking appliances are rated for a single particular input, such as 208 or 230 volts.
Based on the above, there exists a need for a control system that can effectively and efficiently regulate the output of a heating element in a cooking appliance, without the need for an input voltage sensor, an auto transformer or other complicated and costly electronic structure.